LantaoJin commented on pull request #29120: URL: https://github.com/apache/spark/pull/29120#issuecomment-659816264
@manuzhang This is for performance improvement. COALESCE with join will reduce the SMJ operator parallelism. The user case is our internal function: download. Download the query result by one file. We use a COALESCE hint to implement it. But when the join in the query, the parallelism reduced to 1 in the Join operator. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
